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Author: Subject: KNO3 + candle wax => NO reaction ???
metalresearcher
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[*] posted on 21-1-2012 at 13:57
KNO3 + candle wax => NO reaction ???


I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Why ?

Paraffin is a mixture of alkanes ranging from C10 to C20 which is flammable. Why does KNO3 not help ? Other combustible organics (sugar) burn very fast.



[Edited on 2012-1-21 by metalresearcher]
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Neil
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[*] posted on 21-1-2012 at 14:15


The candle wax melts and cools the KNO3. Sugar has a higher melting point point and chars rather then simply melting


Sugar mixed with wax is used as a smoke formula.
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AndersHoveland
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[*] posted on 21-1-2012 at 14:20


There would be a self-sustaining reaction if a large quantity of wax mixed with KNO3, in an adequate ratio, was placed inside an intense fire. But wax has difficulty burning, because as it is heated, it melts into a liquid layer which has a relatively low surface area to combust with any oxygen gas. This is why wax is very difficult to burn without a wick. Also, KNO3 is not really an excellent pyrotechnic oxidizer. In my experience, prills of KNO3 added to burning organic material first seem to take time to get hot and melt before they release oxygen. The prills should be crushed into a fine powder for maximum surface area.
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Mr. Wizard
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[*] posted on 21-1-2012 at 14:27


I agree with Neil.
My best guess is the liquid wax even when melted, keeps the temperature of the KNO3 below the decomposition point, just as the cotton wick of a candle is preserved in a candle flame. When the sugar chars after losing the water in it's make-up, it then allows the heat of the fire to raise it and the nitrate to a point where the reaction proceeds.

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Neil
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[*] posted on 21-1-2012 at 14:35


Quote: Originally posted by AndersHoveland  
There would be a self-sustaining reaction if a large quantity of wax mixed with KNO3, in an adequate ratio, was placed inside an intense fire. But wax has difficulty burning, because as it is heated, it melts into a liquid layer which has a relatively low surface area to combust with any oxygen gas. This is why wax is very difficult to burn without a wick. Also, KNO3 is not really an excellent pyrotechnic oxidizer. In my experience, prills of KNO3 added to burning organic material first seem to take time to get hot and melt before they release oxygen. The prills should be crushed into a fine powder for maximum surface area.



Surface area, for the wax, is not the issue, the low vapor pressure and high boiling point of wax are what limit ones ability to set it on fire. *liquids don't burn* Boiling wax burns and behaves like boiling kerosene.
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[*] posted on 21-1-2012 at 15:31


A bit off topic, but if your looking for a mold-able pyrogen try KNO<sub>3</sub> with peanut butter. I know from experience this works really well with KClO<sub>3</sub> . Even used it in some small paper rockets. When you get the consistency right it is no longer sticky and really easy to work with.

[Edited on 21-1-2012 by Bot0nist]




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AndersHoveland
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[*] posted on 21-1-2012 at 17:24


Mmmm, sounds tasty...

http://2.bp.blogspot.com/-79uoAvAip7E/Tr74bwS05bI/AAAAAAAABl...
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Adas
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[*] posted on 22-1-2012 at 00:36


The wax also increases its volume when heated and boiling temp. of wax is not high enough to release O2 from KNO3 - try adding excess KNO3 (in powder form of course).

As Anders stated before, KNO3 on burning organic material first melts and THEN starts releasing oxygen. And from what I have seen, after it starts releasing the O2, the temperature rises very quickly and the flame on contact surfaces becomes light blue/white. After all O2 is released, the white molten "drop" of KNO3, KNO2 and whatever turns into a black solid in fraction of a second and sticks on the organic material. It is probably K2O. Sometimes you can even smell KCN! That's probably the reaction between NOx released, carbon and K2O.




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[*] posted on 22-1-2012 at 05:24


I bet if there was a barrel of finely ground potassium nitrate impregnated with wax in the correct amount, it would start burning furiously after a while, when the heat builds up in the layers beneath.
Scale of the reaction changes things a lot.




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[*] posted on 22-1-2012 at 07:44


Quote: Originally posted by Endimion17  

Scale of the reaction changes things a lot.


This is so true. It has been accidentally demonstrated many times, often to the demonstrators peril. I have heard many stories of someone trying to make a very large smoke-bomb/volcano and greatly scaling up a sugar+oxidizer or even a zinc/iron+sulfur mix, and instead creating a cascading, exothermic catastrophe.




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[*] posted on 22-1-2012 at 12:21


The wax will definitely melt before the KNO3 breaks down. KNO3 breaks down at something like 700C, and have you ever touched melted wax? Its not even 100C.



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[*] posted on 22-1-2012 at 12:30


No, KNO<sub>3</sub> starts to boil and decompose at just over 380C - 400C, IIRC. I have often boiled it in test tubes and dropped bits of smoldering carbon in it as a demo.

http://en.wikipedia.org/wiki/Kno3

Watch.
http://www.youtube.com/watch?v=Y3Jxhbg0k4c


Oh, and melted wax is one thing. Try boiling wax that's surface has exceeded its auto-ignition temperature and is aflame. This, intimately mixed with decomposing KNO<sub>3</sub> in med to large scale. Could get scary? I would love to conduct some tests. Cheap materials.

[Edited on 22-1-2012 by Bot0nist]




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[*] posted on 22-1-2012 at 12:37


That low 'ey. Well that would explain why I picked it over KClO4 for the same thing with the test tube. Last time I did a frosted mini-wheat. My brother was perplexed at the ammount of energy the box said one had, I thought it was totally reasonable, and then showed him just how much there was (;



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[*] posted on 22-1-2012 at 13:04


Quote:
I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Well try it again ─ this time with an intimate mixture of finely ground oxidiser and sulphur 85/15 and see how that goes!

P
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[*] posted on 23-1-2012 at 09:03


Quote: Originally posted by AirCowPeaCock  
That low 'ey. Well that would explain why I picked it over KClO4 for the same thing with the test tube. Last time I did a frosted mini-wheat. My brother was perplexed at the ammount of energy the box said one had, I thought it was totally reasonable, and then showed him just how much there was (;


If you have previously boiled potassium nitrate in a test tube then I would have assumed you knew its decomposition point lay well below 700C, as even good boro tubes start to fail at over 500C.





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[*] posted on 23-1-2012 at 09:54


Quote: Originally posted by Pulverulescent  
Quote:
I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Well try it again ─ this time with an intimate mixture of finely ground oxidiser and sulphur 85/15 and see how that goes!

P

Many people don't realize the calorie unit used in food is actually a kilogram calorie or 1000 of the gram calories we speak of. It leads to confused thinking and false ideas such as eating frozen food will significantly lower it's caloric intake. ;)
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[*] posted on 23-1-2012 at 11:05


Quote: Originally posted by Pulverulescent  
Quote:
I was just curious. Mixing KNO3 with paraffin candle wax from crushed candles and lighting it.
NOTHING happened except the wax started to burn slowly just as if it were heated without KNO3.

Well try it again ─ this time with an intimate mixture of finely ground oxidiser and sulphur 85/15 and see how that goes!

P


Better hope it has a pretty good flame to flare off the hydrogen sulfide you'd get by boiling wax and sulphur. ;)
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[*] posted on 23-1-2012 at 11:10


Hmm, this got me thinking...what about KNO3 with coal dust?
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[*] posted on 23-1-2012 at 11:20


Quote: Originally posted by Neil  
Better hope it has a pretty good flame to flare off the hydrogen sulfide you'd get by boiling wax and sulphur. ;)


How the hell....?

Quote: Originally posted by Fusionfire  
Hmm, this got me thinking...what about KNO3 with coal dust?


Would behave pretty much as BP




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Neil
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[*] posted on 23-1-2012 at 11:22


too hard to get really good mixin with coal dust. Charcoal on the other hand...
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[*] posted on 23-1-2012 at 11:43


But, Neil, can you explain how paraffin can react with sulfur?? I thought hydrocarbons are pretty inert..



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Neil
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[*] posted on 23-1-2012 at 12:46


Adas, I started answering the above post before yours was posted and thus did not see yours.


Try;

http://www.sciencemadness.org/talk/viewthread.php?action=pri...
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[*] posted on 23-1-2012 at 12:47


How did you mixed the wax with KNO3 ? Poor mixtures leads to little or simple no efficaccy of the oxydizer. Try melting wax with white gasoline, then pouring this into very finely powdered KNO3. Take care then when igniting it cause it may explode in half ?
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[*] posted on 23-1-2012 at 15:07


It's not going to explode. Maybe if one used potassium chlorate, but not with the nitrate.



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[*] posted on 23-1-2012 at 19:51


now in google E book Chemical & metallurgical engineering, Volume 22 page 806
under wax bleaching they describe passing ozone threw molten wax


then of course at nasa
http://science.nasa.gov/science-news/science-at-nasa/2003/28...

they are trying to use wax mixed with the correct oxygen ratio as a nice rocket....



so ozone impregnated wax seems at first neat, but not stoichiometric

the chlorate idea is interesting i must admit
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